4 A minimumboiling azeotrope boils at a temperature that is

4. A minimum-boiling azeotrope boils at a temperature that is lower than either of its components. Why? acetone (bp 56 °C) and cyclohexane (bp 80 °C) form a minimum boiling azeotrope (bp 53 °C); the azeotropic mixture is 75% in acetone (mole %). SKETCH a distillation curve (volume on the x-axis and temperature on the y-axis) to show what you would expect to see should one distill 35 mL of a 50:50 mixture of these liquids. Be as quantitatively accurate as possible (using graph paper).

Solution

In reference to the first part of the question, a minimum-boiling azeotrope refers to the type of azeotropes in which the boiling point of the mixture of liquids is lower than the boiling point of the individual liquids.This is because of the fact that minimum boiling azeotropes occur due to positive deviation from Raoult\'s law. Let us assume two liquids having components A and B.

In case of positive deviation from Raoult\'s law, the constituents have a disaffinity for each other – The molecules of A stick to molecules A and molecules of B to B better than molecules of A stick to B. As a consequence of this , the mixture has less total affinity of the molecules than the pure constituents, and therefore, they more readily escape from the stuck-together phase, which is to say the liquid phase, into the vapor phase. Due to increase of number of molecules in vapor phase, vapor pressure increases, leading to decrease in boiling point. This is visible by the lowering of boiling point of the mixture.

In reference to the second part, I am unable to draw the Volume- Temperature graph since we aren\'t provided with a concentration graph previously from which we could derive the volume of the azeotrope distilled. Please verify and inform me so I could continue with the answer.

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